novice need help with simple fft process

Im sure there is a simple object for this that I have missed, after checking tutorials and help files I am stumped.

I want a simple way to monitor an incoming signal (a piano) and filter all the fundamental frequencies. I am fine with finding the frequencies but need a simple way to filter them out. I thought that a simple e.q would work but it doesn’t have enough bands to filter all the required frequencies. Ideally I would like to do an fft on the incoming signal and subtract the frequencies with the highest amplitude as these will be the fundamental frequencies. If there is a simple way to alter the amplitude of the frequencies as well I will literally jump for joy.